code: def spatial_atleast3d(string_input):
      """
      This function parses a 3-element tuple from a string input.
      The input will be padded with ones, if the length is less than 3.
      """
      output_tuple = int_array(string_input) or (0,)
      if len(output_tuple) < 3:
          # will pad the array with single dimensions
          output_tuple = output_tuple + (1,) * (3 - len(output_tuple))
      return output_tuple
  
file_path: NiftyNet/niftynet/utilities/user_parameters_helper.py
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  import argparse
  import re
  from six import string_types
  from niftynet.utilities.user_parameters_regex import match_array
label_desc: Use image node_id 11 for calling a global function with example usage: spatial_atleast3d(string_input) and returns: output_tuple